Field of the Invention
The present disclosure relates to a method, apparatus and computer-readable medium for switching optical paths, and more particularly to selectively redirecting light to different optical paths.
Description of Related Art
In fluorescence microscopes, there is a need to perform multi-channel imaging, wherein fluorophores emitting light with different wavelengths are sequentially imaged. In multi-channel imaging, a common method of separating the colors is to move different color filters into a light beam passing along an optical pathway. During rapid acquisition, the time required for exchanging filters is often the rate limiting step.
A prior device for moving different color filters into the optical pathway is a filter wheel having a plurality of filters mounted on a carousel, that can be rotated by a motor. The filters effectively select different spectral bands of the light from a light source or from an imaging port of a microscope.
While the filter wheel is conceptually simple, it suffers from several drawbacks. Implementations providing exchange frequencies at or above 30 Hz require that the rotating wheel be carefully balanced to minimize vibration. Changing the spectral bands can be cumbersome, as the changing requires multiple filters be specifically installed in the filter wheel to preserve the balance of the rotating system, or requiring that the whole filter wheel, consisting of the filters and the carousel, be changed.
In addition, the filter wheel is sometimes run at a fixed speed, so changing the effective exposure time of each filer is not possible. Also, the angular momentum of the rotating filter wheel prevents instantaneous stopping or shuttering, and also makes synchronization to an external clock, e.g., a video frame rate clock, difficult. The changes in angular momentum also require significant energy consumption by a driving motor. Finally, because the edge of each filter progressively moves across the width of the light beam as the filter wheel rotates, on-off transitions between the spectral bands are not abrupt, and the transitions include a fixed period of no illumination, the duration of which may not be optimum for all applications. This results in a reduction of the duty cycle and loss of efficiency in energy delivery.
Thus, a need exists for providing efficient optical path switching with improved switching times as well as reduced energy requirements.